Picture of DC Brush Motor for Learning Fun
A friend has a young son who is newly fascinated by motors and electrical things. This Instructable replicates a DC electric demonstration motor I made about two decades ago for my own children. It is offered here for the sake of parents and teachers like my friend who want to help young people build such things and learn, even though an electric motor may not be part of the previous experience of the adult helping the young person. I am purposely using only common hand tools so anyone could make this for his or her own children. The materials used are also very easy to obtain. The final product is designed to work reliably for a long, long time.

If you would like to read a bit about how electric motors work, go to step 19. I did not put that information in the earlier steps because some important concepts must be discussed first.

Materials used--

3 inch finish nail or thin steel rod
1/4 inch steel rod (a 1/4 inch carriage bolt from the hardware store would do and costs very little)
Electrical tape
Cellophane tape
Masking tape
Plastic tubing for a fish tank or medical equipment
Enameled magnet wire about 24 gauge (Spools of magnet wire can be bought at Radio Shack, or magnet wire can be salvaged from a number of devices that no longer work, like old transformers or motors. Be careful about going into an old television set. While you can find wire there, you can also encounter a lethal dose of stored electricity.)
#12 copper wire (from some old household electrical cable)
Thin stranded wire to connect the batteries
Spring clothes pins for holding the connecting wires in contact with the motor
Dowel rod (1/2 inch)
Wood for a base
Thin brass sheet or brass hobby tubing
Steel wool
Epoxy glue
Two ceramic magnets
Hot glue
Batteries or a 3 -- 6 volt AC/DC power supply (2 "D" batteries, a battery holder is suggested)
Motor oil (just a few drops)
Pan head sheet metal screws (two)

Tools used--

Electric hand drill and drill bits (a 1/2 inch spade bit is the best, least expensive option for the larger holes)
Center punch and hammer
Grinding wheel or a concrete face for grinding
Pocket knife
Solder gun or iron
Hot glue gun
Fine-toothed handsaw for wood
Files for metal
Wire cutter
Multi-meter (helpful, but not necessary)
Remove these adsRemove these ads by Signing Up
847MicRoss5 months ago

I just built mine over the weekend. I already know my brushes need some work, but do you think its possible for the magnets to be to strong.

In my opinion I may not have enough of coils on my nail to create enough magnetism that would be = to the amount of magnetism produced by my magnets.

Let me know your thoughts thanks.

Phil B (author)  847MicRoss5 months ago
You can probably wind the armature coils again by splicing the wire on them now, if and when you get access to more wire. You could also try moving the magnets out a little more away from the armature and see if that makes a difference, but they can very quickly come to be too far away from the armature to be effective. As you mentioned, the brushes are a little tricky. Making them press too hard creates too much friction, but making them too loose does not provide enough good contact.

When I was in my early teen years 4-H had plans for one of these motors. In those days cheap cerqmic magnets did not exist. I had to wind a field coil and attach two metal straps bent to fit around the rotation of the armature. I think there were to be 400 turns on the field coil. That was probably 55 years ago. My memory says 150 turns was recommended for the armature, which was four 8 penny nails held in a bundle with cloth electrical tape on a much larger nail acting as the armature shaft. When my kids were young, I replaced the field coil and metal straps with two ceramic magnets. 150 turns of enameled wire worked out well on the armature.

A little motor like this does require a fairly high current supply. If you are using flashlight batteries, they go down quickly and will no longer make the motor spin when oartially depleted. You might also try removing your brushes and making temporary brushes from stranded copper wire you hold in place against the commutator with your two hands, just to see if that makes a difference.

I hope something in this helps. Than you for your comment and for trying this project.
847MicRoss Phil B5 months ago
I built one in my HighSchool electronics class 10+ years ago, we also had pretty detailed instructions. Unfortunately I could not find them anywhere.

I did a little bit of both of your suggestions. My armature had apx 100 coils on the right side, and 100 coils on the left side. (25coiled out then 25 coiled back in, 2x on each side.) I'm using a 1/4" steel rod to wrap my coils around. Although it became magnetized, I feel it could be a little stronger. Adjusting the field magnets helped as well. But my main problem like I mentioned was my brushes.

Is the motor supposed to start as soon as you apply power?
(while holding my brushes) I have to spin my motor to get it going.

My last question for the evening is if my armature axle is extended past (or through) its mounting post, and I attached a small propeller blade to it, would wind propel the motor to generate a SMALL amount of current? To my understanding a generator is motor just working the other way.
Thanks once again for your time.
Phil B (author)  847MicRoss5 months ago

The position of the brushes on the commutator is the key item in whether the motor starts by itself when current is applied. It should start well if the poles of the armature poles are set to be vertical rather than horizontal.

You have an advantage if you built one of these little motors in school. Is the polarity of your field magnets correct? I expect they are correct, but one needs its North Pole facing the armature, while the other needs its South Pole facing the armature. An extra magnet should be attracted to one field magnet and repelled by the other.

A generator is the reverse of a motor. If you have ever pedaled a bicycle with a generator light, you know what a difference there is between pedaling with the generator engaged and not engaged. Your idea should work, but quite a bit of torque could be required from the motor to overcome the friction in the generator and the magnetic drag of the generator.

In regard to the brushes, I found I could hit the sweet spot at which the brushes worked very well, but arcing from the current feeding the armature made it necessary to find a new sweet spot the next time. The arcing depletes the surface of the brushes.

syedsaquib8 months ago
nice i practice it
Phil B (author)  syedsaquib8 months ago
It is fun, especially for children. It does consume batteries.
great and fun thing to make
Phil B (author)  argha halder1 year ago
Thank you. When I was 13 I was completely fascinated by things like this. I wanted to make it simply enough that nearly anyone could make it from what was easily available.
mathieulj2 years ago
Very nice thank you.
Phil B (author)  mathieulj2 years ago
Thank you for looking. I tried to make it so just about anyone could reproduce it for himself from fairly common materials. Kids think it is great.
WWC2 years ago
I Very nice. I have a question about construction. When you soldered the coil leads to the to the brass conductor pieces did you solder the two leads from one coil to the same conductor piece and then the second coil leads to the second conductor to the second conductor piece? So each coil and brass conductor are there own separate circuit with no path between the two?
Phil B (author)  WWC2 years ago
There really is only one coil wrapped partly on one half of the metal core and wrapped partly on the other half of the metal core. The one coil yields two wire ends to be soldered to two brass conductor pieces. Let me know if you still have questions. Thank you for looking and for commenting.
WWC Phil B2 years ago
Ok I think I got it. There is only one wire not two like i was thinking. Thanks for your help!
Phil B (author)  WWC2 years ago
You are correct--only one wire with two ends. When winding, I wound one layer out to the end and back, then I crossed the wire over to the other side and did the same. Then I went back to the first side and wound out and back, then back to the second side again. As I mentioned, it did not balance when I was done. So, I removed about 30 turns from the first side by unwinding wire and wound all of it back on the second side. There is no magic in the number 30. It was just a first attempt at moving enough wire from one side to the other to make the armature balance.
Wow!!! Brings back memories :)
Excellent instructable and very detailed as always Phil.
Thank you
Thank you, Steli. Kiteman recently published an Instructable on how to write and publish Instructables. In it he mentioned school classrooms sometimes use an Instructable for teaching purposes. I hesitated to do this until my encounter with my friend whose son is suddenly interested in electricity combined with Kiteman's comment. I do not know if you had 4-H Clubs on Cyprus when you were growing up, but I was in one in my home state of Iowa here in the USA. They had some project bulletins for things people might exhibit at the local county fair. One was a DC motor using a commutator and brushes, but that was in the days before cheap ceramic magnets and those plans called for electro-magnets in the field. A key feature of those plans was that all of the steel parts were from a couple of sizes of common nails held together with electrical tape to make the armature and the field, as well as the supports for the armature. I made one, but modified it quite a bit. I bent some strap iron for the field. That motor worked, too. I think my brothers and I powered it with the transformer from a toy electric train.  I expect you must have built something similar as a boy.
I remember when I was a kid we did some similar projects in science class, but soon after I changed my direction towards what we call the classical studies, ancient Greek and Latin languages, History, Philosophy etc., so I can’t claim to remember today much of that science stuff. But I do remember few main things of it LOL that’s why I commented that it brings back some memories :)
It is too bad you had to choose between languages, etc. and science interests. My high school offered only a couple of years of French. I was planning to become a pastor and would need to study German, Latin, Koine' Greek, and biblical Hebrew. Someone told me those who do well in science and mathematics also do well in languages. I liked science and mathematics, and found I also enjoy languages.
Dipankar2 years ago
Very good Phil, Beautifully explained.
I would get tired from writing such a big article, but you are great.
Phil B (author)  Dipankar2 years ago
Thank you. I really enjoy explaining something so someone else can use it.
rimar20002 years ago
Perfect as always, Phil!
Phil B (author)  rimar20002 years ago
Thank you, Osvaldo. I am glad you enjoyed it.